2001 Cherokee Sport 4.0 I-6 Oil Pressure Fluctuation - JeepForum.com
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post #1 of 6 Old 08-16-2008, 08:43 PM Thread Starter
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2001 Cherokee Sport 4.0 I-6 Oil Pressure Fluctuation

I noticed today while driving through a parking lot that my oil pressure was dropping to between 15-20 psi. While driving at hwy speeds it is upwards of 40 psi. I haven't noticed the pressure dropping like this before but it didn't seem normal.

I been reading on the net about a propensity for cracked heads on the Cherokee. I had a new radiator put in a couple of months ago and I can't seem to keep the coolant level up. I had it re-filled about 5 days ago and the overflow tank is already empty again. I pulled the dip stick and the oil doesn't appear normal, it has more the consistency of water than oil. I need to dump the oil tomorrow to get a better look.

Also, I have been smelling coolant both inside of the vehicle, and outside after getting out in the garage. No leakage on the floor however.

Is a cracked head likely here? Can someone advise what needs to done to verify my head is cracked, and what is a reasonable repair cost to remedy this situation. How many hours of labor is typical and what would be the cost of the parts?
Thanks much.

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post #2 of 6 Old 08-16-2008, 10:37 PM
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It could be as simple as a blown head gasket. If that gasket goes, you'll be leaking coolant into your heads and oil and coolant will be mixing. That's probably where your smell is coming from. I'm not saying this is the problem, but it's one of the likely ones. Are you getting any smoke from the exhaust, or lots of excess water coming out of it? Head gaskets run about 100.00 bucks or so. Could also be the reason your oil pressure is fowling up. My 01 did the oil pressure craziness for awhile, changed the sending unit, seafoamed it, and it's working just fine again.
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post #3 of 6 Old 08-16-2008, 11:07 PM
Matt Gertsch
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That pressure range is normal. Your oil will look like a chocolate milkshake if there are head problems.

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post #4 of 6 Old 08-17-2008, 08:47 AM
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The oil pressure fluctuation is normal for the 4.0 engine. Mine has done that as long as I can remember. I run Mobil One 5 W 30 in it.
As far as the coolant smell you may have spilled some in engine compartment when you changed radiator.
But, if you are losing coolant you can look for these things.
Look under carpet on passenger side. If heater core is leaking it will be going there.
Also if you put in stock plastic tank - aluminum center radiator it could be leaking at the tank seams or at hose connections. Wash the hoses and radiator area very well with water and let dry. Then let it run to temp gets up and look for leaks.
I put in all aluminum radiator when mine started seaping. Best money I have ever spent.
If you blew head gasket the oil will have a milky look. If it is clear no problem.
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post #5 of 6 Old 08-18-2008, 07:01 PM
It's the crank sensor!
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Oil pressure fluctuations normal as mentioned by others. If you continue to lose coolant, it's going somewhere and if it's not leaking it (INSPECTION) then it's burning it. A pressure test or a leakdown test can give you some real clues there...Sounds like the visual inspection of the oil would be enough for me to do some hardcore testing to determine root cause. Good Luck!

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post #6 of 6 Old 08-24-2008, 06:56 AM Thread Starter
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I believe my cooling system is now functioning normally, after replacing the radiator again, as well as the hoses and water pump. There is a long story behind my problem. My car was damaged on the front end during a hit and run about 3 years ago. As it turns out, the repair shop had put stop leak in the radiator instead of replacing it. I found out about this recently when the radiator was last replaced about 3-4 months ago. Unfortuately my mechanic didn't care to check out that my system was functioning correctly, and did not put coolant in, only water. I had a radiator specialist work through the issues yesterday. My new radiator was already leaking, and I still had mud clogging the system. Why anyone would replace the radiator without flushing that stuff out I'll never understand. He even looked at it again 2 weeks ago and didn't even advise me that the coolant wasn't even circulating! The radiator specialist I went to yesterday found that the impellers on the water pump were corroded down to knife edges. It was a pretty pitiful sight.

Thanks to all who responded.
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